Process for the production of diazotype copies



United States Patent i PROCESS FOR THE PRUDUCTIDN OF Y DIAZOTYPE CGPIES No Drawing. Application September 10, 1952, Serial No. 303,939

Claims. (Cl, 95-438) Our copending application Serial No. 276,061, filed 'March 11, 1952, describes'a process for the production of diaZotype copies in which use is made of one-component diazo film layers, the para-aminobenzene-diazo compoundof which upon exposure in water forms a product that is active, analkaline intermediate treatment taking place between exposure and development.

The images obtained according to that process have a gradation which, specifically in the dark areas of the image, causes better reproduction of the half tones than would have been obtained if the alkaline intermediate treatment had been omitted.

It'has' been found important for practical purposes to vary and/or control the effect obtained according to the process of said copending application. By a method capable of achieving that control it is possible, in addition=to the richer reproduction of details produced by the half tone efiect, though partly at the expense of the latter, to introduce to some extent into the image to be produced the strong contrasts so characteristic of ordinary diazotype printing.

According to the invention of the present application, we have discovered that the control of. the half tone effect referred toabove is obtained when in the process .accordingto said copending application an azo coupling component is added to the copy during the alkaline intermediate treatment. If the intermediate treatment is carried out with an alkaline liquid A, it is possible to dissolve in the said liquid a given portion of the azo coupling component provided with a view to the development proper, with the aid of the second liquid B, and omit this portion from the liquid B. By the selection of the quantities one can thus control the extent to which one desires to obtain the half tone effect.

' Substances Whichin general have sufficient coupling activity for the practical application of thin-layer development include p-diazo-diphenylamine, p-diazo-ethyl-benzylaniline, p-diazo-di-normal-butylaniline, p-diazo-ortho- 'chlorodiethyl-aniline, the p-diazo-2,5-dialkoxy-acyl anilides, and many others. The p-diazo2,5-dialkoxy-acy1 anilides are very active, and even suitable for development at pH about 7.

Examples of diazo compounds which in practice are preferably not used for diazotype printing with thinlayer development, because they have insufiicient coupling activity, are pdiazo-aniline, p-diazo-monomethylaniline and p-diazo-dimethyl-aniline. Compounds such as p-diazo-diethylaniline and p-diazo-dipropyl-aniline are on the borderline for practical application by thin-layer development.

As azo coupling components having suflicient coupling activity for. thin-layer development there may be mentioned beta-naphthol, phloroglucinol, resorcinol, lphenyl-3-methyl-5-pyrazolone (very active) and acetoacetanilide; azo components with insuflicient coupling activity are phenol and 2,3-di-hydroxy-naphthalene-6- sulphonic acid.

By the term diazo film layer as used herein is meant a special type of diazo layer. The generic term diazo layer is also used when the diazo compound is simply spread out on the fibers of a paper surface as a dried-up coating, perhaps in the-form of a very thin, uneven and possibly discontinuous diazo surface. A diazo film layer in accordance with the present invention has the char-,

acter of a true layer of measurable thickness. A diazo film layer need not be equally thick throughout; it may, for example, show a relief. Such a diazo film layer comprises material which will be referred to hereinafter as film-forming material.

The diazo film layers must be resistant to treatment with the thin layer of aqueous developer, i. e., the filmforming material employed must not present any serious difiiculty when treated with an aqueous liquid, for example by reason of melting, dissolving or becoming objectionably sticky as is the case with layers of gum, alkyl cellulose, soft gelatine and similar substances. On the other hand, it must be capable of readily accepting and absorbing the thin layer of developer.

The diazo film layer will usually be mounted on a support; in special cases it may, however, also be independent.

By exposure of various p-aminobenzene-diazo compounds certain products (hereinafter to be called photochemical decomposition products) are formed which are capable of reacting at room temperature with aqueous solutions of diazo compounds with a pH of over 7, whereas the'photo-chemical decomposition products of other paminobenzene-diazo compounds do not have this effect, or only slightly so. The said action, when it takes place, proceeds more rapidly the higher the pH of the solution and takes place to a measurable extent, for example, at pHs ranging from 9 to 10. x The action of the photochemical decomposition products of the various p-aminobenzene-diazo compounds may be compared by testing them with the aid of a compoundoflthis class which itself undergoes only very slight changes,-if any, when stored under the conditions hereinafter described. It has been found that p-diethylaminobenzene-diazonium chloride satisfies this requirement. If a 0.002 normal solution of this compound in Water, to which sodium carbonate has been added to bring the pH to 9.5, is allowed to stand for 15 minutes at 18 C. (without exposure to light), the content of diazo, compound in the solution is but very slightly altered. The decrease of the diazo content is found to be about 2% and this serves as the control test.

The action of the photochemical decomposition products of p-aminobenzene-diazo compounds may be tested by adding the photochemical decomposition products of the p-aminobenzene-diazo compounds to be tested to a azonium chloride solution, and brought to a pH of 9.5

by the addition of sodium carbonate. The mixture is now allowed to stand for 15 minutes at 18 C. after which the remaining quantity of p-diethylaminobenzene-diazonium compound is determined.

The results of tests witha number of diazo compounds are set out in the following table:

Percentage Photochemical decomposition product-oi of decomposition p-dlazo-ortho-ehlorodiethylaniline 3 p-dlazo-meta-chlorodiethylnnlline 50 p-diazocthylbenzy e 80 p dtazo-diethylaruline 80 p-diazo-di-normnl-butylnnilin 80 p-diazodi-nonnal-amylanlllne. 80 p-diazo-dl-normal-hexylanlline 80 in which X is an anion, while R1 and R2 are alkyl radicals having together l0, 11 or 12 C atoms, each alkyl radical containing at least 4 and at most 7 C atoms, and not more than one of the two having a side chain attached to the alpha C atom.

The intermediate treatment may be followed almost immediately by the development with a thin layer of a developer containing an active azo coupling component. The intermediate treatment is carried out according to the thin-layer method, preferably with a layer of liquid that is as thin as possible, for example of 7 g. per in. 'During the subsequent development the-previous alkaline treatment will also be taken into account with regard to the alkaline content of the-developer. The alkaline intermediate treatment may even be carried out in such a manner that the total quantity of alkali required .for the development is added to the copy, in which case the .alkali can be omitted from the developer, which has the advantage that the latter will .thus be lessliable to deterioration.

For the production of diapositives and cinematographic films the diazo film layer is mounted on a clear filmshaped support. In this form the invention constitutes an entirely new contribution to the application or diazotype printing for these purposes. Particularly strong images with good gradations in the dark half tones are obtained when the diazo content of the diazo film layer is between 0.8 and 2:0 millimols per mi For the film-forming material for the diazo film layer it is advantageous to choose a hydrolysed cellulose ester with .an average number of acyl groups attached to the OH groups between and 1.5 -(triacetate==3.0). Preferably a hydrolysed cellulose acetate is taken, but other esters, mixtures of esters or mixed esters, for example acetate-butyrates, are also very suitable. Particularly good results are obtained when the film-forming material of the diazo film layer consists of a cellulose ester with an acyl content increasing from the accessible side inwards, the portion of the layer that is insoluble in boiling dry acetone being at least 3 g. and at most 15 g. per m? One may, however, also use other-more or less hydrophilicmaterials, for example not too soft gelatine, partially hydrolysed polyvinyl esters, cellulose film (cellulose hydrate) mounted on a support, for the "diazo film layer. l I

Example Paper of 210 g. per m., which is coated on one side with a cellulose acetate (about 53 of combined acetate acid) layer of about 10 1. thickness, which is applied on the paper by means of an adhesive and deacylated to a depth of about 4,11. to an acetyl content which increases from the accessible side inwards and which, calculated as combined acetic acid, averages about 20% (which corresponds to an average number of acetyl groups attached to the OH groups of about 0.7), is impregnated .on the deacylated side of the cellulose acetate layer for 30 seconds with the following solution:

22 g. zinc chloride double salt of -diamdi-normalhexylaniline 3 g. citric acid 3 g. ammonium chloride 50 cm. ethyl alcohol (96%) 900 cm. water.

The excess of liquid is removed irom the cellulose acetate surface, and the material is subsequentlydried. It contains about 0.8 millimol of diazo compound per m. After exposure under a diapositive the copy is treated with about 9 g. per m? of the following liquid A:

10 g. phloroglucinol '10 g. resorcinol 10g. thiourea 50 g. sodium thiosulphate -1 g. potassium'salt of hydroquinonemonosulphonic acid 3 g. sodium salt of isopropylnaphthalene-sulphonic acid 3 g. sodium salt of mono-Z-ethylhexylester of sulphuric acid 1000 cm. water.

A black image is obtained, the gradation of which .is softer than would have beenobtained, if the alkaline intermediate treatment described above (liquid A) had been omitted and the development had exclusively been lefiected with liquid B to which the alkali from liquid A had been added, while the gradation is less soft than would have been obtained, if the phloroglucinol had been omitted from liquid A.

What we claim is:

l. A process for the production of diazotype copies which comprises selectively exposing .to light a .one- .component diazo film layer material comprising a diazo film layer that is suitable for development with a liquid and contains a film-forming material and a p-aminobenzene diazo compound that yields an active photochemical decomposition pro'ductin the sense that a quantity of the solution obtained upon totally decomposing by light all of said compound contained in a Weakly acid 0.004 11 aqueous solution of said compound, 'When mixed with an equal quantity of a 0.004 n aqueous solution of -p-diethylamino benzene diazonium chloride, and allowed to stand at 18 C. and at a pH of about 9.5, decomposes at least half of the amount of diazonium chloride in the latter solution within 15 minutes, said diazo compound upon exposure being capableof reacting with its photochemical decomposition product under alkaline conditions with the eifect that the part of "said diazo compound so reacted no longer will couple with an azo was, 1

coupling component to give a dyestutf; so that by the exposing step said diazo compound is only partially decomposed atcertain areas-of said material; rendering the exposed diazo film layer alkaline to bring about the aforesaid reaction at saidcertain areas and while so doing treating said layer witha substantial but minor part of the total amount of am coupling component to be used for the developmentof said layer; and thereafter developing an image in the treated diazo film layer by applying to said layer a developer liquid containing the remainder of said amount of azo coupling component; the ratio of the amount of alkaline substance to the amount of azo coupling component in the liquid applied in said step of rendering said layer alkaline being greater than the ratio thereof in said developer liquid.

2. A process as described in claim 1 wherein the treatment of the exposed diazo film layer between'said exposing step and said developing step is effected by applying to said layer a thin layer of an alkaline liquid containing an azo coupling component.

3. A process as described in claim 1 and for the production of diapositives and cinematographic films, wherein said diazo film layer has a transparent film support.

4. A process as described in claim 1, said diazo film layer containing from 0.8 to 2.0 millimols of said p-aminobenzene diazo compound per square meter thereof.

5. A process as described in claim 1, the film-forming material of said diazo film layer consisting of an at least partially hydrolyzed cellulose ester wherein the average number of acyl groups attached to OH groups is from to 1.5.

6. A process as described in claim 1, the film-forming material of said diazo film layer consisting of an at least partially hydrolyzed cellulose ester, the acyl content of said material increasing progressively from the accessible side of said diazo film layer toward the interior thereof, said diazo film layer comprising from 3 to 15 grams of hydrolyzed matter insoluble in boiling dry acetone per square meter of said layer.

7. A process as described in claim 1 wherein the treatment of the exposed diazo film layer between said exposing step and said developing step is effected by applying to said layer an alkaline liquid containing substantially all the alkali required for the development of the image, the developer liquid being substantially free of alkali.

8. A process for the production of diazotype copies, which comprises selectively exposing to light a onecomponent diazo film layer material comprising a diazo film layer that is suitable for development with a liquid and contains a film-forming material a p-aminobenzene diazo compound of the formula:

in which X is an anion and R1 and R2 are alkyl radicals together having a total of to 12 carbon atoms, each alkyl radical having at least four and at most seven carbon atoms, and not more than one of the two alkyl radicals having a side chain attached to the alpha carbon atom, said diazo compound upon exposure being capable of reacting with its photochemical decomposition product under alkaline conditions with the elfect that the part of said diazo compound so reacted no longer will couple with an azo coupling component to give a dyestulf; so that by the exposing step said diazo compound is only partially decomposed at certain areas of said material; rendering the exposed diazo film layer alkaline to bring about the aforesaid reaction at said certain areas and while so doing treating said layer with a substantial but minor part of the total amount of azotreated diazo film layer by" applying to said layer a develo'per'liquid containing'the remainderof said am'dnng I of azo coupling component; the ratio of the amount of alkaline substance to the amount of azo coupling component in the liquid applied in said step of rendering said layer alkaline being greaterthan the ratio thereof in said developer liquid.

9. A process for the production of diazotype copies,

which comprises selectively exposing to light a onecomponent diazo film layer material comprising a diazo film layer that is suitable for development with a liquid and contains a film-forming material and a salt of p-diazo-di-n hexylaniline, said diazo compound upon exposure being capable of reacting with its photochemical decomposition product under alkaline conditions with the effect that the part of said diazo compound so reacted no longer will couple with an azo coupling component to give a dyestuff; so that by the exposing step said diazo compound is only partially decomposed at certain areas of said material; rendering the exposed diazo film layer alkaline to bring about the aforesaid reaction at said certain areas and while so doing treating said layer with a substantial but minor part of the total amount of azo coupling component tobe used for the development of said layer; and thereafter developing an image in the treated diazo film layer by applying to said layer a developer liquid containing the remainder of said amount of azo coupling component; the ratio of the amount of alkaline substance to the amount of azo coupling component in the liquid applied in said step of rendering said layer alkaline being greater than the ratio thereof in said developer liquid.

10. A process for the production of diazotype copies, which comprises selectively exposing to light a onecomponent diazo film layer material comprising a diazo film layer that is suitable for development with a liquid and mounted on an opaque support and contains filmforming material consisting essentially of a partially hydrolyzed cellulose ester of which the acyl content increases from the accessible side of said layer toward the interior thereof, said ester having an average number of acyl groups attached to OH groups of from 0 to 1.5, said diazo film layer also comprising, per square meter thereof, from 0.8 to 2.0 millimols of a p-aminobenzene diazo compound of the following formula:

in which X is an anion and R1 and R2 are alkyl radicals together having a total of 10 to 12 carbon atoms, each alkyl radical having at least four and at most seven carbon atoms, and not more than one of the two alkyl radicals having a side chain attached to the alpha carbon atom, said diazo compound upon exposure being capable of reacting with its photochemical decomposition product under alkaline conditions with the effect that the part of said diazo compound so reacted no longer will couple with an azo coupling component to give a dyestuff; so that by the exposing step said diazo compound is only partially decomposed at certain areas of said material; applying to the exposed film layer a thin layer of an alkaline liquid containing substantially all of the alkali required for the development of the image-and also containing a substantial but minor part of the total amount of azo coupling component to be used for the development of said layer to bring about the aforesaid reaction at certain areas; and thereafter developing an image in the diazo film layer by applying to said layer a thin aqueous layer, substantially free of alkali, containing the remainder of said amount of azo .Rcferences Cited in the file of this patent coupling component; the ratio of the amount of alkaline I p ATES PATENTS substance to the amount of azo coupling component in 8 V d G Se 1 19 l the substances applied in said step of rendering said layer {i 3 2: 235:: 2 1 5 1 v a aline being substantially greater than the ratio thereof 2,528,460 V Von Glahn Oct- 31' 1950 in said thin aqueous layer. 

1. A PROCES FOR THE PRODUCTION OF DIAZOTYPE COPIES WHICH COMPRISES SELECTIVELY EXPOSING TO LIGHT A ONECOMPONENT DIAZO FILM LAYER MATERIAL COMPRISING A DIAZO FILM LAYER THAT IS SUITABLE FOR DEVELOPMENT WITH A LIQUID AND CONTAINS A FILM-FORMING MATERIAL AND A P-AMINOBENZEND DIAZO COMPOUND THAT YIELDS AN ACTIVE PHOTOCHEMICAL DECOMPOSITION PRODUCT IN THE SENSE THAT A QUANTITY OF THE SOLUTION OBTAINED UPON TOTALLY DECOMPOSING BY LIGHT ALL OF SAID COMPOUND CONTAINED IN A WEAKLY ACID 0.004 N AQUEOUS SOLUTION OF SAID COMPOUND, WHEN MIXED WITH AN EQUAL QUANTITY OF A 0.004 N AQUEOUS SOLUTION OF P-DIETHYLAMINO BENZENE DIAZONIUM CHLORIDE, AND ALLOWED TO STAND AT 18* C. AND AT A PH OF ABOUT 9.5, DECOMPOSES AT LEAST HALD THE AMOUNT OF DIAZONIUM CHLORIDE IN THE LATTER SOLUTION WITHIN 15 MINUTES, SAID DIAZO COMPOUND UPON EXPOSURE BEING CAPABLE OF REACTING WITH TIS PHOTOCHEMICAL DECOMPOSITION PRODUCT UNDER ALKALINE CONDITIONS WITH THE EFFECT THAT THE PART OF SAID DIAZO COMPOUND SO REACTED NO LONGER WILL COUPLE WITH AN AZO COUPLING COMPONENT TO GIVE A DYESTUFF; SO THAT BY THE EXPOSING STEP SAID DIAZO COMPOUND IS ONLY PARTIALLY DECOMPOSED AT CERTAIN AREAS OF SAID MATERIAL; RENDERING THE EXPOSED DIAZO FILM LAYER ALKALINE TO BRING ABOUT THE AFORESAID REACTION AT SAID CERTAIN AREAS AND WHILE SO DOING TREATING SAID LAYER WITH A SUBSTANTIAL BUT MINOR PART OF THE TOTAL AMOUNT OF AZO COUPLING COMPONENT TO BE USED FOR DEVELOPMENT OF SAID LAYER; AND THEREAFTER DEVELOPING AN IMAGE IN THE TREATED DIAZO FILM LAYER BY APPLYING TO SAID LAYER A DEVELOPER LIQUID CONTAINING THE REMAINDER OF SAID AMOUNT OF AZO COUPLING COMPONENT; THE RATIO OF THE AMOUNT OF ALKALINE SUBSTANCE TO THE AMOUNT OF AZO COUPLING COMPONENT IN THE LIQUID APPLIED IN SAID STEP OF RENDERING SAID LAYER ALKALINE BEING GREATER THAN THE RATIO THEREOF IN SAID DEVELOPER LIQUID. 